Crack stop barrier and method of manufacturing thereof

ABSTRACT

A wafer is disclosed. The wafer comprises a plurality of chips and a plurality of kerfs. A kerf of the plurality of kerfs separates one chip from another chip. The kerf comprises a crack stop barrier.

This is a divisional application of U.S. application Ser. No.12/898,468, entitled “Crack Stop Barrier and Method of ManufacturingThereof” which was filed on Oct. 5, 2010 and is incorporated herein byreference.

TECHNICAL FIELD

The present invention relates generally to the manufacture ofsemiconductor devices and more particularly to the manufacture chips byseparating semiconductor wafers and semiconductor wafers having crackstop barriers.

BACKGROUND

Dozens or hundreds of integrated circuits are typically manufactured ona single semiconductor wafer. The semiconductor wafer comprises chips ordies in which the integrated circuits are located, and kerfs or scribelines which separate the individual chips. The individual chips arediced by sawing the wafer along the kerf. The individual chips are thentypically packaged, either separately or in a multi-chip module.

SUMMARY OF THE INVENTION

In accordance with an embodiment of the present invention, a wafer isdisclosed. The wafer comprises a plurality of chips and a plurality ofkerfs. A kerf of the plurality of kerfs separates one chip from anotherchip. The kerf comprises a crack stop barrier.

In accordance with an embodiment of the present invention, a method ofmanufacturing chips is disclosed. The method comprises applying a chipdesign to chips of a wafer and applying a kerf design to the kerf of thewafer. The kerf design comprises a crack stop barrier. The methodfurther comprises dicing the wafer to separate the chips.

The foregoing has outlined rather broadly the features and technicaladvantages of embodiments of the present invention in order that thedetailed description of the invention that follows may be betterunderstood. Additional features and advantages of embodiments of theinvention will be descried hereinafter, which form the subject of theclaims of the invention. It should be appreciated by those skilled inthe art that the conception and specific embodiments disclosed may bereadily utilized as a basis for modifying or designing other structuresor processes for carrying out the same purpose of the present invention.It should be realized by those skilled in the art that such equivalentconstructions do not depart from the spirit and scope of the inventionas set forth in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 shows a wafer;

FIG. 2 shows a conventional kerf junction;

FIG. 3 shows a top view of an embodiment of a kerf junction;

FIG. 4 shows a top view of an embodiment of a kerf junction;

FIG. 5 shows a top view of an embodiment of a kerf junction;

FIG. 6 shows a top view of an embodiment of a kerf junction;

FIGS. 7 a and 7 b show top views of embodiments of a kerf junction;

FIG. 8 shows a cross sectional view of a crack stop barrier.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the presently preferred embodiments arediscussed in detail below. It should be appreciated, however, that thepresent invention provides many applicable inventive concepts that canbe embodied in a wide variety of specific contexts. The specificembodiments discussed are merely illustrative of specific ways to makeand use the invention, and do not limit the scope of the invention.

The present invention will be described with respect to embodiments in aspecific context, namely a crack stop barrier in a kerf or on asemiconductor wafer.

FIG. 1 shows a wafer 100 comprising a plurality of chips or dies 200 anda plurality of kerfs or scribe lines 300. Each chip 200 may be separatedfrom other chips 200 by kerfs or scribe lines 300. The intersections ofthe kerfs 300 may form kerf junctions 400.

The kerfs 300 may comprise test features such as optical alignmentstructures, process control monitoring structures, and/or reliabilitycontrol monitoring structures. The test features may be short featureshaving a structure shorter than a chip length or long features havingstructures longer than a chip length. The long test features may extendin or beyond a kerf junction 400 or a plurality of kerf junctions 400.The test features may extend beyond several junctions 400 and may bearranged along a long or short side of several chips.

FIG. 2 shows a detail of a conventional wafer 100. Four chips 210-213are shown. The chips 210-213 are separated by kerfs 310 and 311. Thekerfs 310 and 311 form a kerf junction 410. Each chip 210-213 maycomprise an inner region 214-217 within the respective chip 210-213. Theinner region 214-217 may be an integrated circuit region. The integratedcircuit region 214-217 may be enclosed or surrounded by a seal or crackstop ring located in a peripheral region 218-221 of the chip 210-213.The crack stop ring is supposed to prevent cracks or delamination frompropagating toward the integrated circuit 214-217 of the chips 210-213while the chips 210-213 are separated by sawing the kerf. The kerfjunction 410 may be a square or a rectangle.

FIG. 2 shows a shaded region 510. The shaded region 510 shows thepropagation of cracks while the chips 210-213 are separated. As can beseen from FIG. 2, the crack stop rings of the peripheral regions 218-221may prevent delamination or propagation of the cracks toward theintegrated circuits region 214-217 along a long side 225 and along ashort side 226 of chip 210, for example. However, the crack stop ringsof the peripheral regions 218-221 may not be able to preventdelamination or propagation of cracks at a corner 227 of the chip 210.The corner 227 of the chip 210 may be more vulnerable to delaminationand cracks because the corner 227 may be more exposed to separationforces than the long side 225 and/or the short side 226 of chip 210. Ina particular example, the corner 227 may be exposed to separation forcesnot only from one direction but from two directions.

A problem may occur when the corner 227 cannot stop propagations ofcracks. Cracks may enter the inner regions 214-217 of the chips 210-213damaging the integrated circuit regions 214-217 and leading to devicefailures. The cracks can disrupt conductive lines rendering theintegrated circuits 214-217 inoperable. The cracks can also allowmoisture and other contaminants to enter into the integrated circuitregion 214-217 of the chips 210-213, causing corrosion and otherproblems.

Thus, what is needed in the art is an arrangement that prevent crackspropagating into the integrated circuit regions 214-217 of the chips210-213 while separating the chips 210-213.

FIG. 3 shows a top view of an embodiment of a detail of a wafer 100.FIG. 3 shows four chips, i.e. a first chip 230, a second chip 240, athird chip 250 and a fourth chip 260. The chips 230-260 may be memorychips or logic chips. For example, the chips 230-260 may be DRAM chips,non-volatile memory chips, microcontroller chips and the like. FIG. 3further shows two perpendicular scribe lines 320, 330. The two scribelines 320, 330 form a kerf or scribe line junction 420. Two crack stopbarriers 610, 620 are arranged in the scribe line junction 420. Thecrack stop barriers 610, 620 are arranged parallel to the first kerf 320direction and orthogonal to a second kerf 330 direction. The crack stopbarriers 610, 620 are arranged on opposite sides of the kerf junction420. The crack stop barriers 610, 620 may block a propagation of cracksalong the second kerf 330 direction. The crack stop barriers 610, 620may not block a propagation of cracks along the first kerf 320direction.

The first crack stop barrier 610 is arranged between the first chip 230and a second chip 240, and the second crack stop barrier 620 is arrangedbetween the third chip 250 and the fourth chip 260. The first crack stopbarrier 610 may be in line with a long side 231 of the first chip 230and a long side 241 of the second chip 240, and the second crack stopbarrier 620 is in line with a long side 251 of the third chip 250 and along side of 261 the fourth chip 260. The first crack stop barrier 610is an extension of corners 233, 243 of a first chip 230 and a secondchip 240. The second crack stop barrier 620 is an extension of corners253, 263 of a third chip 250 and a fourth chip 260. The first crack stopbarrier 610 is orthogonal to a short side 232 of the first chip 230 anda short side 242 of the second chip 240, and the second crack stopbarrier 620 is orthogonal to a short side 252 of the third chip 250 anda short side 262 of the fourth chip 260. In one embodiment the crackstop barrier 610, 620 may be arranged in line with a short side 232-262of the chip 230-260 and orthogonal to a long side 231-251 of the chip230-260.

In one embodiment the crack stop barrier 610, 620 may be in line with orparallel to features 270 located in and along the first kerf 320 or thesecond kerf 330. The features 270 may be test features such as opticalalignment structures, process control monitoring (pcm) structures,and/or reliability control monitoring (rcm) structures. If the features270 are located in and along the first kerf 320 then the crack stopbarriers 610, 620 may be in line with the first kerf 320. If thefeatures 270 are located in and along the second kerf 320 then the crackstop barriers 610, 620 may be in line with the second kerf 330. In oneembodiment crack stop barriers 610, 620 may only be arranged in linewith kerfs 320, 330 comprising features 270 longer than a length of onechip or features 270 crossing the junction 420.

The crack stop barrier 610 may be physically connected to the crack stopbarriers 235, 245 of the chips 230, 240, and the crack stop barrier 620may be physically connected to the crack stop barriers 255, 265 of thechips 250, 260. In one embodiment the crack stop barriers 610, 620 mayblock the entire width of the second kerf 330.

The crack stop barriers 610, 620 may be continuous lines. Alternatively,the crack stop barriers 610, 620 may be staggered discrete lines orjagged lines. The crack stop barriers 610, 620 may be sawtooth or zigzaglines. The crack stop barriers 610, 620 may be made from a solidmaterial. A solid material may be a conductive or semiconductivematerial such as a metal, silicon or polysilicon, or, alternatively, adielectric material such as silicon dioxide or high-k dielectrics.

The crack stop barriers 610, 620 may be a single barrier line or aplurality of barrier lines. For example, crack stop barriers 610, 620each may be two barrier lines. Crack stop barrier 610 may have the samenumber of barrier lines as crack stop barrier 620. Alternatively, crackstop barrier 610 may have different numbers of barrier lines as crackstop barrier 620. For example, crack stop barrier 610 may comprise asingle barrier line while crack stop barrier 620 may comprise a dualbarrier line.

The crack stop barriers 610, 620 may comprise a width of about 3 μm toabout 12 μm. The crack stop barrier lines of the crack stop barriers610, 620 may comprise a width of about 0.5 μm to about 4 μm. The crackbarrier lines may comprise a width of about 1 μm to about 3 μm.

FIG. 4 shows a top view of another embodiment of crack stop barriers610, 620. The crack stop barriers 610, 620 may only block parts of theentire width of the second kerf 330. The crack stop barrier 610 may notbe physically connected to the crack stop barriers 235, 245 of the chips230, 240 and may be arranged in a distance or a gap from the crack stopbarriers 235, 245 of the chips 230, 240. For example, the distancebetween the crack stop barriers 235, 245 of the chips 230, 240 and thecrack stop barrier 610 may be about 1 μm to about 3 μm. Alternatively,the gap may be about 1.5 μm to about 2 μm. Crack stop barrier 620 may beplaced at a same or a similar distance from the crack stop barriers 255,265 of the chips 250, 260 as crack stop barrier 610 from the crack stopbarriers 235, 245. Alternatively, the crack stop barrier 620 may beplaced at a different distance from the crack stop barriers 255, 265 ofthe chips 250, 260 than crack stop barrier 610 from the crack stopbarriers 235, 245.

FIG. 5 shows a top view of another embodiment of crack stop barriers610, 620. The crack stop barriers 610, 620 are located at leastpartially within the kerf junction 420. The crack stop barriers 610, 620may be located at a peripheral region of the square or the rectangle ofthe kerf junction 420. The crack stop barriers 610, 620 may be locatedin the first kerf 320 and in the second kerf 330.

The crack stop barrier 610 may be placed at a first distance d₁ from anedge 233 of the first chip 230 and a second distance d₂ form the edge243 of the first chip 240. Distance d₁ and distance d₂ may be the sameor may be different. For example, distance d₁ may be about 2 μm to about5 μm. The crack stop barrier 620 may be placed at a third distance d₃from an edge 253 of the third chip 250 and a fourth distance d₄ form theedge 263 of the fourth chip 260. Distance d₃ and distance d₄ may be thesame or may be different. Distance d₁ and distance d₃ may be the same ormay be different, and distance d₂ and distance d₄ may be the same or maybe different. All the distances d₁-d₄ may be the same or different.

The lengths of the crack stop barriers 610, 620 may be shorter, as largeas or larger than the width of the kerf 330. The lengths of the crackstop barriers 610, 620 may be the same or may be different.

FIG. 6 shows a top view of an embodiment of crack stop barriers 610-640.The crack stop barriers 610-640 are arranged along a perimeter of thekerf junction 420. The crack stop barrier 610 may be physicallyconnected to the crack stop barriers 235, 245 of the chips 230, 240, andthe crack stop barrier 620 may be physically connected to the crack stopbarriers 255, 265 of the chips 250, 260. The crack stop barrier 630 maybe physically connected to the crack stop barriers 236, 256 of the chips230, 250, and the crack stop barrier 640 may be physically connected tothe crack stop barriers 246, 266 of the chips 240, 260. In oneembodiment the crack stop barriers 610-640 may block the entire widthsof the kerfs 320, 330.

In another embodiment crack stop barriers 610-640 may only block partsof the entire width of the kerfs 320, 330. The crack stop barriers610-640 may not be physically connected to the crack stop barriers235-266 of the chips 230-260 and may be arranged in a distance or a gapfrom the crack stop barriers 235-266 of the chips 230-260. In oneembodiment some of the crack stop barriers 610-640 may be physicallyconnected to the crack stop barriers 235-265 of the chips 230-260, andsome of the crack stop barriers 610-640 may not be physically connectedto the crack stop barriers 235-265 of the chips 230-260.

FIG. 7 a shows a top view of an embodiment of crack stop barriers610-640. The crack stop barriers 610-640 are located at least partiallywithin the kerf junction 420. The crack stop barriers 610 and 620 maycomprise saw-tooth lines (FIG. 7 b). The crack stop barriers 610-640 maybe located at a peripheral region of the square or the rectangle of thekerf junction 420. The crack stop barriers 610-640 may be located in thefirst kerf 320 and in the second kerf 330. The crack stop barriers 610,620 may be arranged parallel to the first kerf 320 direction, and thecrack stop barriers 630, 640 may be arranged orthogonal to the firstkerf 320 direction. The crack stop barriers 630, 640 may be arrangedparallel to the second kerf 330 direction, and the crack stop barriers610, 640 may be arranged orthogonal to the second kerf 330 direction.Similar to the discussion above with respect to FIG. 5, the crack stopbarriers 610-640 may have the same distances from the edges 233-263 ofthe chips 230-260 or different distances from the edges 233-263 of thechips 230-260.

In the particular example of FIG. 7 a, the lengths of the barriers 610,620 are larger than the width of the kerf 330, and the lengths of thebarriers 630, 640 are shorter than the width of the kerf 320. In oneembodiment the lengths of the crack stop barriers 610-640 all may beshorter than the widths of the kerfs 320, 330. In one embodiment thelengths of the crack stop barriers 610, 620 are the same and the lengthsof the crack stop barriers 630, 640 are the same. In another embodimentthe ratio (length of the crack stop barrier 610-640 relative to thewidth of the kerf 320, 330) is the same but the lengths of the crackstop barriers 610-640 are different. In yet another embodiment thelengths of the crack stop barriers 610-640 may be shorter, as large asor larger than the width of the kerfs 320, 330.

The crack stop barriers 610-640 may comprise the same material, designs,widths, and distances as described for the crack stop barriers withrespect to FIG. 3.

FIG. 8 shows a cross-sectional view of an embodiment of a crack stopbarrier 600 in a kerf or scribe line 300. The crack stop barrier 600 maybe made of several isolation layers 650-660. Each isolation layer maycomprise an isolation material and a crack stop material or solidmaterial. The isolation material may be silicon dioxide or a low-kdielectric, for example. The crack stop material may be a conductivematerial such as a metal, e.g. aluminum (Al), copper (Co), tungsten (W),or polysilicon. Alternatively, the crack stop material may be adielectric material such as silicon-dioxide, silicon nitride, or ahigh-k dielectric.

FIG. 8 shows a substrate 640. The substrate 640 may includemono-crystalline silicon, gallium arsenide (GaAs), germanium (Ge),silicon-on-insulator (SOI), or any other substrate material. Thesubstrate 640 is a wafer and may comprise kerf regions.

A first isolation layer 650 is formed over the substrate 640 by knownmethods. The first isolation layer 650 is patterned to form contactholes or trenches. The contact holes or trenches may be filled with asolid material to form contacts or plugs 651.

A second isolation layer 652 is deposited and patterned to form trenchesfor depositing solid material lines 653. The solid material lines 653 ofthe second isolation layer 652 extend into and out of the plane of thepage. A third isolation layer 654 is formed and patterned to create viasor trenches which are then filled with a solid material to form plugs orcontacts 655. A fourth isolation layer 656 is deposited and patterned toform trenches for depositing solid material lines 657. The solidmaterial lines 657 of the fourth isolation layer 656 extend into and outof the plane of the page. The plugs or contacts 655 physically connectthe solid material lines 657 of the fourth isolation layer 656 with thesolid material lines 653 of the second isolation layer 652.

Advantageously, multiple levels of isolation layers 650-658 may bedeposited to form the crack stop barrier 600. The crack stop barrier 600may be created by alternating forming isolation layers 652-656 havingsolid material lines 653-657 and isolation layers 650-656 having plugs,contacts or trenches 651-659 comprising the solid material. The crackstop barrier 600 may be passivated by a passivation layer 660.

FIG. 8 shows only one row of plugs or contacts 655 physically connectingsolid material line 653 to solid material line 657. In one embodimenttwo or more parallel rows of plugs or contacts 655 may be formed tophysically connect solid material line 653 to solid material line 657(not shown). In one embodiment the crack stop barrier 600 may be a dualbarrier line. In one embodiment each barrier line of the dual barrierline crack stop barrier 600 may comprise the same material, width, anddesign as the single line crack stop barrier. In another embodiment eachline of the dual barrier line of the crack stop barrier 600 may comprisedifferent materials, widths and/or designs. Alternatively, the crackstop barrier 600 may be a single barrier line or a multi barrier line.

The crack stop barrier 600 may comprise a pyramid type structure with awidth of the solid material lines 653-657 being smaller in the toplevels than in the bottom levels. For example, first solid materiallines 653 may comprise a first thickness, and second solid materiallines 657 may comprise a second thickness. The second thickness is thesame or less than the first thickness. The crack stop barrier 600 maycomprise cube type structure with a width of the solid material lines653-657 being the same in all layers.

The crack stop barrier 600 is formed on a wafer. The semiconductor wafer640 may comprise kerf regions 300 and chip or die regions 200. A chipdesign may be applied or processed through a back end of line (BEOL)manufacturing process to the chip regions 200. A kerf design may beapplied or processed through a BEOL manufacturing process to the kerfregions 300. The chip design and the kerf design may be two differentlycreated designs.

The chip design may comprise crack stop barriers and the kerf design maycomprise crack stop barriers. The chips, processed according to the chipdesign, may comprise a crack stop barrier along an outer rim of thechips. The crack stop barriers of the chips may form a ring around anintegrated circuit. The crack stop barrier may seal the chip protectingit against cracks and moister.

The kerf design may comprise crack stop barriers in a kerf 300, in akerf junction 400 or in the vicinity of a kerf junction 400. In oneembodiment the crack stop barrier may be arranged orthogonal to a firstkerf direction and parallel to a second kerf direction. In oneembodiment the crack stop barriers may be arranged orthogonal to a firstkerf direction and orthogonal to a second kerf direction. The crack stopbarriers may be arranged along opposite sides of a kerf junction. Thecrack stop barrier may be arranged along a perimeter of the kerfjunction 400. The crack stop barrier may be arranged at a distanceinside the perimeter of the kerf junction 400 or may be arranged at adistance outside the perimeter of the kerf junction 400.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the invention as defined by the appended claims. For example,many of the features and functions discussed above can be implemented ina capacitor manufacturing process having a lower electrode, a dielectricand an upper electrode. As another example, it will be readilyunderstood by those skilled in the art that the novel process steps maybe applied to any structure which has two conductive layers next to oneanother and that the process steps may be varied while remaining withinthe scope of the present invention.

Moreover, the scope of the present application is not intended to belimited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the disclosure of the present invention, processes,machines, manufacture, compositions of matter, means, methods, or steps,presently existing or later to be developed, that perform substantiallythe same function or achieve substantially the same result as thecorresponding embodiments described herein may be utilized according tothe present invention. Accordingly, the appended claims are intended toinclude within their scope such processes, machines, manufacture,compositions of matter, means, methods, or steps.

What is claimed is:
 1. A wafer comprising: a kerf junction comprising afirst kerf and second kerf, the first kerf having a first main directionand the second kerf having a second main direction, the first kerfseparating a first chip and a second chip on a first side of the secondkerf and the first kerf separating a third chip and a fourth chip on asecond side of the second kerf; a first continuous crack stop barrierhaving a third direction, wherein the third direction is different thanthe first main direction, wherein the first continuous crack stopbarrier is located in the kerf junction, and wherein the firstcontinuous crack stop barrier extends over a width of the first kerf butdoes not connect to the first chip and the second chip; a secondcontinuous crack stop barrier having a fourth direction, wherein thefourth direction is different than the first main direction, wherein thesecond continuous crack stop barrier is located in the kerf junction,and wherein the second continuous crack stop barrier extends over thewidth of the first kerf but does not connect to the third chip and thefourth chip; and a third continuous crack stop barrier having a fifthdirection, wherein the fifth direction is different than the second maindirection, wherein the third continuous crack stop barrier is located inthe kerf junction, and wherein the third continuous crack stop barrierextends across a majority but not the entire width of the second kerf.2. The wafer of claim 1, wherein the third direction and the fourthdirection are parallel to the second main direction.
 3. The wafer ofclaim 1, wherein the kerf junction further comprises a test feature. 4.The wafer of claim 3, wherein the test feature is parallel to the secondmain direction, and wherein the test feature is larger than a width ofthe second kerf.
 5. The wafer of claim 3, wherein the test feature is anoptical alignment structure.
 6. The wafer of claim 3, wherein the testfeature is a process control monitoring (pcm) structure.
 7. The wafer ofclaim 3, wherein the test feature is a reliability control monitoring(rcm) structure.
 8. The wafer of claim 1, wherein the first continuouscrack stop barrier comprises a saw-tooth line.
 9. The wafer of claim 1,wherein the first continuous crack stop barrier extends across amajority but not the entire width of the first kerf.
 10. The wafer ofclaim 1, wherein the first continuous crack stop barrier is larger thanthe width of the first kerf.
 11. The wafer of claim 1, wherein the firstcontinuous crack stop barrier comprises a cube type structure.
 12. Thewafer of claim 1, wherein the first continuous crack stop barriercomprises a pyramid type structure.
 13. The wafer of claim 1, furthercomprising a fourth continuous crack stop barrier having a sixthdirection, wherein the sixth direction is different than the second maindirection, wherein the fourth continuous crack stop barrier is locatedin the kerf junction, and wherein the third continuous crack stopbarrier extends across a majority but not the entire width of the secondkerf.
 14. The wafer of claim 13, wherein the fifth direction and thesixth direction are parallel to the first main direction.
 15. A wafercomprising: a kerf junction comprising a first kerf and second kerf, thefirst kerf having a first main direction and the second kerf having asecond main direction, the first kerf separating a first chip and asecond chip on a first side of the second kerf and the first kerfseparating a third chip and a fourth chip on a second side of the secondkerf; and a first continuous crack stop barrier having a thirddirection, wherein the third direction is different than the first maindirection, wherein the first continuous crack stop barrier is located inthe kerf junction, and wherein the first continuous crack stop barrierextends over a width of the first kerf but does not connect to the firstchip and the second chip; a second continuous crack stop barrier havinga fourth direction, wherein the fourth direction is different than thefirst main direction, wherein the second continuous crack stop barrieris located in the kerf junction, and wherein the second continuous crackstop barrier extends over the width of the first kerf but does notconnect to the third chip and the fourth chip; a third continuous crackstop barrier having a fifth direction, wherein the fifth direction isdifferent than the second main direction, wherein the third continuouscrack stop barrier is located in the kerf junction, and wherein thethird continuous crack stop barrier does not cross over the firstcontinuous crack stop barrier or the second continuous crack stopbarrier; and a fourth continuous crack stop barrier having a sixthdirection, wherein the sixth direction is different than the second maindirection, wherein the fourth continuous crack stop barrier is locatedin the kerf junction, and wherein the fourth continuous crack stopbarrier does not cross over the first continuous crack stop barrier orthe second continuous crack stop barrier, wherein the first to fourthcontinuous crack stop barrier comprise solid material structures in anisolation layer stack.
 16. The wafer of claim 15, wherein the thirddirection and the fourth direction are parallel to the second maindirection, and wherein the fifth direction and the sixth direction areparallel to the first main direction.